Cocoa beans have high levels of flavanols, which are plant chemicals thought to protect from oxidative stress and other types of damage. A recent study reported that drinking cocoa with high levels of flavanols increased blood oxygenation in the brain and improved performance on a complex cognitive task [1].
These new findings come from a randomized placebo-controlled trial of 17 healthy young adults [1]. Participants were given a low- or high-flavanol cocoa drink, then breathed room air with added carbon dioxide (5%), designed to challenge the brain to increase cerebral blood flow and oxygenation of the blood. This compensatory response to the challenge is called “cerebrovascular reactivity”. Participants also underwent various cognitive tests ranging in difficulty levels after drinking low- or high-flavanol cocoa. To control for any bias, the study was carried out in a double-blind manner, wherein participants and the researchers did not know which cocoa treatment (low- or high-flavanol) the participants were drinking.
When participants drank the high-flavanol cocoa drink before the carbon dioxide challenge, they had a faster and greater “cerebrovascular reactivity” as measured by increased cerebral blood flow and blood oxygenation. Also, individuals who showed improved “cerebrovascular reactivity” with high-flavanol cocoa also showed improvements in a complex cognitive task. However, there was no improvement in performance on simple cognitive tasks after drinking high- or low-flavanol cocoa.
It is worth noting that not everyone benefited from the high-flavanol cocoa. Four out of the 17 participants already had high “cerebrovascular reactivity” at baseline and did not show further enhancements in “cerebrovascular reactivity” or in cognitive performance after drinking high-flavanol cocoa.
While this was a well-designed and well-controlled study, it was a small study testing a single serving of cocoa aimed at identifying acute effects of flavanols. It is not clear yet how long this effect lasts, or if these flavanols need to be taken frequently to have sustained effects on cognitive functions. It also remains to be seen whether cocoa flavanols when used long-term could slow cognitive decline or decrease dementia risk. Larger, longer studies are needed to answer these questions.
Still, these findings are encouraging and in line with other research findings suggesting that cocoa increases blood flow to the brain [2] and may slightly improve select cognitive functions [3]. If you are considering incorporating more cocoa into your diet, remember that flavanol content varies depending on the type of product; dark chocolate has higher levels of flavanols than milk and white chocolate. It is also worth paying attention to whether the cocoa product has undergone “Dutch” processing, or alkalization, which reduces the acidity and bitterness, but also reduces the amount of flavanols by 60 to 90 percent [4]. And moderation is key as some cocoa products like chocolate bars often have high fat and calories, which may offset the health benefits.
To learn more about other research on cocoa and chocolate, see our rating.
Yuko Hara, PhD, is Director of Aging and Alzheimer's Prevention at the Alzheimer's Drug Discovery Foundation. Dr. Hara was previously an Assistant Professor in Neuroscience at the Icahn School of Medicine at Mount Sinai, where she remains an adjunct faculty member. Her research focused on brain aging, specifically how estrogens and reproductive aging influence the aging brain's synapses and mitochondria. She earned a doctorate in neurology and neuroscience at Weill Graduate School of Medical Sciences of Cornell University and a bachelor's degree in biology from Cornell University, with additional study at Keio University in Japan. Dr. Hara has authored numerous peer-reviewed publications, including articles in PNAS and Journal of Neuroscience.
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